Bioactive peptides refer to the peptides compounds beneficial to life activity of organisms or having physiological effects, which are peptides fragments with smaller molecular weight obtained by enzyme digestion of macromolecules of proteins. Compared to proteins, the active peptides are small molecules but with high biological activities, and a small amount of peptides can play an extremely important and remarkable physiological role. Since Hughes et al first reported that small peptides with an activity similar to morphine were found in animal tissues in 1975, a variety of bioactive peptides have been isolated from animals, plants and micro-organisms. It has been proved by research that various bioactive peptides products obtained from natural protein enzymolysis can be easily absorbed by the human body, and the specific structures and properties of which generally exhibit a variety of physiological functions including anti-oxidation, anti-fatigue, lowering blood fat, lowering blood pressure, strengthening immunity and the like. Preparing bioactive peptides by enzymolysis of proteins from nature sources has the advantages of wide raw material sources, no toxic and side effects, capable of scale production, low price, etc. Therefore, in recent years the research and development of bioactive peptides have become a major development direction in the global food and nutrition-related research fields.
Hypertension is a disease seriously threatening to human health. The global hypertension impact report issued in 2007 gave warning that the number of people suffering from hypertension has an increasing trend in the world, and currently stands at 1 billion; if no effective measures were taken, by 2025, the world would have 1.56 billion people suffering from the disease. The number of hypertensive patients may increase by 80% in some countries, including China. Angiotensin I-converting enzyme (ACE) is a kind of multifunctional dipeptide carboxypeptidase, which can convert angiotensin I without physiological activity into angiotensin II with blood pressure rising effect, and can also degrade Bradykinin into inactivation fragments, which leads to vasoconstriction, and results in elevated blood pressure. Inhibiting ACE activity by ACE inhibitors to hinder the conversion of angiotensin I into angiotensin II has become the primary means of hypertension prevention.
According to disclosures in some reports, more than 30 kinds of synthetic ACE inhibitors have entered into clinical research or applications. Although these synthetic inhibitors have significant blood pressure-lowering effect, they can also cause many side effects, such as cough, allergy, rash, edema, cardiac arrhythmia and kidney damage, etc. Therefore, the demand for researching and developing safer and more effective ACE inhibitors are becoming more and more urgent.
With the rise of the “return to nature” philosophy and the biologically active peptides research, extracting safe, effective, no side-effect ACE inhibitory peptides from natural animal and plant resources has become a hot spot in the research of hypertension prevention. So far, the edible food-borne peptides put into industrial production have mostly been early researched soybean peptides, milk peptides, marine peptides, etc.
As one of the three major food crops, corn plays an important role in the world's food structure. Corn germ protein powders, as the main byproduct in the wetting process of corn starch, are rich in protein, also contain inorganic salts and a variety of vitamins and other ingredients, but they are underused. In China, for example, corn germ protein powders are mainly used for feed industry or are naturally discharged. Annual natural discharge of corn protein is up to 0.1 million tons, which not only is a waste of valuable food resources, but also causes serious pollution to environment.
Currently, there is little research on obtaining bioactive peptides from the corn germ protein powders. According to the present invention, the technology of protein enzymolysis is used to establish an industrialized method for obtaining corn antihypertensive active peptides from corn germ protein powders, and it has been proved that the obtained products have definite characteristic components and biological activity, which have great practical value and economic benefits to the full use of the rich resources of corn as well as to develop functional foods and nutrition health care products.